The present invention relates to an optical wavelength multiplexing and dividing device that is used in, for example, an optical wavelength multiplex transmission. Background of the invention.
Recently, in a wavelength multiplex optical transmission system, an attempt has been carried out, in which the number of optical transmissions is increased by increasing the degree of multiplex in wavelengths. In order to achieve the objective, it is necessary to prepare an optical wavelength multiplexing and dividing device that is able to multiplex and divide a plurality of signal lights whose wavelength interval is lnm or less. For example, in a wavelength multiplexed transmission at a wavelength band of 1.55 xcexcm, an optical wavelength multiplexing and dividing device is demanded, which is able to multiplex and divide a plurality of signal lights whose wavelength interval is 0.8 nm (100 GHz interval in terms of frequency).
A diffraction grating is available as an example of the optical wavelength multiplexing and dividing device. In an optical wavelength multiplexing and dividing device in which a prior art diffraction grating is employed, there is a limitation in the number of diffractions that can be used, wherein sufficient dispersion cannot be obtained. Therefore, although it was impossible to decrease the wavelength interval to 1 nm or less, Japanese Laid-Open Patent Publication No. 65588-1989 proposed an optical wavelength multiplexing and dividing device which improves the wavelength resolution by using an array type waveguide diffraction grating as a diffraction grating and can narrow the wavelength interval.
As shown in FIG. 6(a), the proposed optical wavelength multiplexing and dividing device has a waveguide chip in which a waveguide pattern is formed on a substrate 1. The optical wavelength multiplexing and dividing device is constructed as follows; that is, the abovementioned waveguide pattern is composed so the input type slab waveguide 3 which functions as a first slab waveguide is connected to the outgoing side of optical input waveguides 2 juxtaposed in a plurality, a plurality of juxtaposed array waveguides 4 are connected to the outgoing side of the input side slab waveguide 3, an output side slab waveguide 5 which functions as a second slab wave guide is connected to the outgoing side of a plurality of array waveguides 4, and a plurality of juxtaposed optical output waveguides 6 are connected to the outgoing side of the output side slab waveguide 5.
The array waveguides 4 are composed so as to have different lengths from each other, and propagate light introduced from the input side slab waveguide 3. In addition, the optical input waveguides 2 and optical output waveguides 6 are provided so as to correspond to the number of a plurality of signal lights having different wavelengths from each other, which are divided by, for example, an optical wavelength multiplexing and dividing device. Although the array waveguides 4 are usually provided in a plurality, for example, 100 in number, the number of these respective waveguides 2, 4 and 6 is simply illustrated in FIG. 6(a) for the sake of simplification of the drawing.
Transmission side optical fibers (not illustrated) are connected to the optical input waveguides, in which wavelength-multiplexed light is introduced. The light introduced through the optical input waveguides 2 into the input side slab waveguide 3 is widened by its diffraction effect and is made incident into a plurality of array waveguides 4 for propagation therein. The light propagated in the respective array waveguides 4 reaches the output side slab waveguide 5, wherein the light is condensed and outputted into the optical output waveguides 6. In the light propagation, since the lengths of the respective array waveguides 4 are different from each other, a deviation in the individual optical phases arises after the light propagates in the respective array type waveguides 4, whereby the wave plane of the converged light is inclined in line with the deviation amount, and the angle of inclination determines a light condensing position. Therefore, by forming the optical output waveguides 6 at the light condensing position, light having different wavelengths can be outputted wavelength by wavelength from the optical output waveguides 6.
For example, as shown in FIG. 6(b), a signal (signal light) 1, having a wavelength xcex, which is condensed through the output side slab waveguide 5 is condensed at the incident ends 7 of the output side waveguides 6 shown with a mark #1, and a signal 2 having a wavelength (xcex+xcex94xcex), which is condensed through the output side slab waveguide 5 is condensed at the incident ends 7 of the output side waveguides 6 shown by a mark #2. A signal 3 having a wavelength (xcex+2xcex94xcex), which is condensed through the output side slab waveguide 5 is condensed at the incident ends 7 of the output side waveguides 6 shown by a mark #3. Thus, light is made incident from the respective input ends 7 into the optical output waveguides 6, and is outputted from the outgoing ends 8 of the optical output waveguides 6 through the respective optical output waveguides 6.
Therefore, as shown in FIG. 7, by connecting optical fibers 10 for optical output to the outgoing ends 8 of the respective optical output waveguides 6, it is possible to separate and pick up light of the abovementioned respective wavelengths through the optical fibers. Further, in the abovementioned optical wavelength multiplexing and dividing device, the arraying pitch Ø of the outgoing ends 8 of the optical output waveguides 6 is formed to be approx. 250 xcexcm, which is equal to the diameter Ø of the optical fibers 10 so that the optical fibers 10 can be easily connected to the outgoing ends 8 of the optical output waveguides 6. And the arraying pitch of the outgoing ends 8 of the optical output waveguides 6 is formed greater than that of the incident ends 7 of the optical output waveguides 6.
In an optical wavelength multiplexing and dividing device of the array type waveguide diffraction grating, since the wavelength resolution is proportional to a difference (xcex94L) in length of the respective array waveguides 4 which constitute diffraction gratings, it becomes possible to multiplex and divide wavelength-multiplexed light of a narrow wavelength interval, which could not be achieved by any prior art diffraction grating, by designing the xcex94L to be a large value.
However, in an optical wavelength multiplexing and dividing device of such an array waveguide diffraction grating, a deviation arises in the wavelength characteristics of an optical wavelength multiplexing and dividing device due to unevenness in the film thickness of a produced waveguide pattern, waveguide widths, refractive index, etc. If such a deviation occurs, signal light of the respective wavelengths, which is condensed through the output side slab waveguide 5, is not normally condensed at the incident ends 7 of the optical output. waveguides 6 shown at, for example, #1, #2 and #3, and the light is condensed at a deviated position shown at 9 in FIG. 6(b). The deviation of the condensing position reaches xc2x10.5 nm or so at most in terms of wavelength, wherein since light of the respective wavelengths is condensed at a position far from the incident ends 7 of the optical output waveguides 6, it is impossible to make the light of the respective wavelengths into the optical output waveguides 6.
In addition, as a means for reducing the problem of the deviation in wavelengths divided by such an optical wavelength multiplexing and dividing device, such a method is proposed, which shifts a wavelength condensed at the incident ends 7 of the optical output waveguides 6 by combining a temperature controlling device to a waveguide chip and utilizing a temperature dependency of the refractive index of a material which forms an optical waveguide. However, if this method is used, since it is possible to control a passing wavelength in only a remarkably narrow range of, for example, xc2x10.05 nm, an optical wavelength multiplexing and dividing device, in which the wavelength to be divided deviates beyond the range, becomes defective. Therefore, even though such a method is used, an optical wavelength multiplexing and dividing device in which such an array waveguide diffraction grating is utilized has a low yield rate in production, and this results in an increase in production cost of an optical wavelength multiplexing and dividing device using such an array waveguide diffraction grating, and this becomes a factor by which practical application thereof is suppressed.
The present invention was developed in order to solve the abovementioned problems and shortcomings, and it is therefore an object of the invention to provide an optical wavelength multiplexing and dividing device which scarcely becomes defective even though a deviation arises in the wavelength characteristics resulting from unevenness in production, thereby improving the production yield ratio thereof.
In order to achieve the above object, the present invention is featured in that the optical wavelength multiplexing and dividing device is constructed as follows; That is, the first aspect of the invention is an optical wavelength multiplex and dividing device which has a waveguide pattern, in which a first slab waveguide is connected to the outgoing side of optical input waveguides juxtaposed in a plurality, a plurality of juxtaposed array waveguides, having different lengths from each other, which propagate light taken out from the first slab waveguide, are connected to the outgoing side of the first slab waveguide, a second slab waveguide is connected to the outgoing side of the plurality of array waveguides, and a plurality of juxtaposed optical output waveguides are connected to the outgoing side of the second slab waveguide, wherein a plurality of optical signals, having different wavelengths from each other, which are inputted from the optical input waveguides are caused to propagate with deviations in phase given wavelength by wavelength by the array waveguides, are made incident into optical output waveguides having different wavelengths from each other for each of the wavelengths, and are outputted from optical output waveguides having different wavelengths from each other, wherein the respective incident ends of the plurality of optical output waveguides are provided at a predicted light condensing position of light of the respective wavelengths which are predicted to be condensed through the above second slab waveguide, and a predicted light condensing correcting position where the light condensing position is deviated with the abovementioned light condensing predicted position.
Further, the second aspect of the invention is featured in that, in addition to the construction according to the first aspect, an arraying pitch of the outgoing ends of optical output waveguides is made one fractional plurality with respect to the diameter o optical fibers connected to the outgoing end side of the optical output waveguides, and the corresponding optical fibers are connected to an alternative plurality of the optical output waveguides or several alternatives thereof.
In addition, the third aspect of the invention is featured in that, in addition to the abovementioned first and second constructions, where optical output waveguides secured at the abovementioned light condensing predicted position are made into the first optical output waveguides, and the optical output waveguides secured at the light condensing prediction corrected position are made into the second optical output waveguides, the incident ends of these first and second optical output waveguides are alternately provided at equal intervals.
Further, the fourth aspect of the invention is featured in that, in addition to the first or second construction, where optical output waveguides secured at the abovementioned light condensing predicted position are made into the first optical output waveguides, and the optical output waveguides secured at the light condensing prediction corrected position are made into the second optical output waveguides, these first and second optical output waveguides are alternately provided while the incident ends of the first optical output waveguides are arrayed at equal pitches and the incident ends of the second optical output waveguides are also arrayed at equal pitches, the interval between the incident ends of the first optical output waveguides and the incident ends of the second optical output waveguides which are located at one side adjacent to the corresponding first optical output waveguides is made different from the interval between the incident ends of the first optical output waveguides and those of the second optical output waveguides located at the other side adjacent to the corresponding first optical output waveguides.
Further, the fifth aspect of the invention is featured in that, in addition to the first or second construction, where the optical output waveguides secured at the abovementioned light condensing predicted position are made into the first optical output waveguides, and the optical output waveguides secured at the light condensing prediction corrected position are made into the second optical output waveguides, the respective incident ends of the first optical output waveguides are arrayed at equal pitches, and a plurality of the second optical output waveguides are arrayed in the pitches of the corresponding first optical output waveguides.
In the invention thus constructed, the respective incident ends of a plurality of optical output waveguides are provided at the light condensing predicted position of the respective wavelengths where light is predicted to be condensed through the second slab waveguides after the light is given a phase deviation for each of the wavelengths and is caused to propagate by the array waveguides, and at the light condensing prediction corrected position where the light condensing position is deviated with respect to the light condensing predicted position.
Therefore, according to the invention, for example, when the film thickness of the waveguide pattern, waveguide widths, refractive index, etc., are produced almost as per design, light of the respective wavelengths, which is condensed through the second slab waveguides can be made incident into the optical output waveguides having the incident ends formed at the light condensing predicted position. On the other hand, where the film thickness of the waveguide pattern, waveguide width, refractive index, etc., are not produced as per design, and a deviation occurs in the wavelength characteristics of an optical wavelength multiplexing and dividing device, light of the respective wavelengths can be made incident into optical output waveguides having the incident ends formed at the light condensing prediction corrected position, depending on the amount of deviation.
As described above, by selectively connecting optical fibers, etc., to the output ends of either the optical output waveguide of the light condensing predicted position or the light condensing prediction corrected position and picking up light outputted through the optical output waveguides, the probability of picking up light of the respective wavelengths, which is condensed through the second slab waveguides, through the optical output waveguides can be improved.
Therefore, according to the present invention, even though a deviation in the wavelength characteristics results from unevenness in production, the products scarcely become defective, whereby the production yield ratio can be further improved.
In addition, in such a structure where the arraying pitch of the outgoing ends of optical output waveguides can be formed to one fractional plurality with respect to the diameter of optical fibers connected to the outgoing end side of the corresponding waveguides, when connecting optical fibers to the outgoing end side of the optical output waveguides, the optical fibers are, as a whole, positioned in relation to the optical output waveguides as optical fiber arrays, wherein, for example, by causing these optical fiber arrays to slide as a whole, it is possible to connect the optical fibers to an alternative plurality of the optical output waveguides or to several alternatives of optical output waveguides. Therefore, the optical fiber connection to the optical output waveguides can be further facilitated, wherein it becomes possible to easily form an optical wavelength multiplexing and dividing device.
Further, in such a construction in which the incident ends of the first and second optical output waveguides are alternately provided at equal pitches where optical output waveguides secured at the light condensing predicted position are made into the first optical output waveguides and optical output waveguides secured at the light condensing prediction corrected position are made into the second optical output waveguides, it is possible to very easily form an optical wavelength multiplexing and dividing device, which brings various excellent effects described above.
Further, if the arraying pattern of the optical output waveguides is made so that the incident ends of the first and second optical output waveguides are alternately provided at equal pitches where optical output waveguides secured at the light condensing predicted position are made into the first optical output waveguides and optical output waveguides secured at the light condensing prediction corrected position are made into the second optical output waveguides, it is possible to very easily form an optical wavelength multiplexing and dividing device, which brings various excellent effects described above.
In addition, in such a construction where the incident ends of the first optical output waveguides are arrayed at equal pitches with the first and second output waveguides alternately provided, the incident ends of the second optical output waveguides are arrayed at equal pitches, and the intervals between the incident ends of the first optical output waveguides and the incident ends of the second optical output waveguides adjacent to the first optical output waveguides are made different from each other, an optical wavelength multiplexing and dividing device can be regarded as a xe2x80x9cpassed productxe2x80x9d in both a case where the light condensed through the second slab waveguide is deviated to the incident end side of the second optical output waveguide at one side adjacent to the first optical output waveguide, a case where the light is deviated to the incident end side of the optical output waveguide at the other side adjacent to the first optical output waveguides if the light is deviated from the first optical output waveguides. Therefore, it is possible to further decrease the ratio at which optical wavelength multiplexing and dividing devices become defective even though a deviation in the wavelength characteristics results from unevenness in production. Therefore, the production yield ratio thereof can be further improved.
Further, in a construction where the incident ends of the first optical output waveguides are alternately arrayed at equal pitches and a plurality of the second optical output waveguides are arranged in the pitches of the corresponding optical output waveguides, the optical wavelength multiplexing and dividing device can be made into a xe2x80x9cpassed productxe2x80x9d even in a case where the light condensed through the second slab waveguide is deviated to either of the second optical output waveguides between the pitches of the first optical output waveguides. Therefore, even though a deviation in the wavelength characteristics results from unevenness in production, the ratio at which the products become defective can be further reduced, and the production yield thereof can be further improved.